lecture 11 Flashcards
(28 cards)
sensation
the ability to transduce, encode and perceive information generated by stimuli arising form both external and internal environment
what do afferent sensory signals do
convert the energy associated with mechanical forces, light, sound waves, electrical field into neural signals and convey info to brain
what information to afferent sensory signals send
qualitative and quantitative aspects of stimulus and sometimes the location
polymodal receptors
naturally sensitive to more than one stimulus modality
adequate stimulus
preferred or most sensitive stimulus
- point at which stimulus starts to be detectable
nociceptors
sensitive to extremely strong stimuli or various kinds of temperature, pressure and chemicals
often polymodal
dynamic range
range of intensities for which receptors can encode stimuli
threshold detection
weakest stimulus that produces a response in a receptor 50% of the time
saturation
top of the dynamic range where all available sensory transfusing proteins have been stimulated or neurons can’t fire any faster
how do sensory neutrons code stimulus intensities
through changes in AP frequency or graded potential change(the stronger a stimuli the higher frequency of depolarization and the more NT release)
range fractionation
groups of receptors that can work together to increase dynamic range without decreasing sensory discrimination
relationship between stimulus and AP frequency
large range- large changes in stimulus causes a small change in AP frequency = large dynamic range poor sensory discrimination
small range: small changes in stimulus causes a large range of AP frequency = small dynamic range high sensory discrimination
3 broad classes of encoding receptors
phasic - AP once at beginning or end of stimulus (changes in stimulus not duration)
tonic non adapting- produce AP as long as stimulus continues
tonic slow adapting - AP frequency decreases if stimulus is maintained
projection of pain/temp and mechano
mechanosensory: ipsilateral
pain/temp: contralatteral
difference between generator/spike potential
all sensory neutrons have generator potential but the ones who fire AP also have spike potential - if it gets high enough to fire an AP
- for receptors that fire spikes nothing is detected if stimulus is too weak to generate a spike
receptive field
area of skin surface over which stimulation results in a significant change in AP rate
dermatomes
body surface mapped to specific segments of spinal cord
- cervical, thoracic, lumbar, sacral
where does adaptation happen
in the channel OR in the sensory organ
merkel- superficial
form and texture perception - 9mm/100cm/
spatial acuity- 0.5mm and 5Hz
threshold 8-30um
messner - superficial
motion grip detection/ grip control - 22mm/150cm
spatial acuity- 3mm and 50Hz
threshold around 2-6um
pacinian- deep
perception of distant events through vibrations (tool use) - entire finger/hand- 20cm
spatial acuity- 10+mm and 200Hz
threshold 0.01-0.08um
ruffini- deep
tangential force: hand shape or motion direction - 60mm / 1-cm
spatial acuity - 7mm and 0.5Hz
threshold 40-300um
what cells are affected when reading braille
merkel
two types of proprioceptors
muscle spindle- length info
Golgi tendon organ- tension info
